1) Field on the Invention
The present invention relates to a polyisocyanate prepolymer with excellent weather resistance, high strength, excellent mechanical properties including flexibility and elongation, good curing, low viscosity and high security which is useful to various sealing materials, water proof agents, coating materials, coating agents, adhesives and paving materials, particularly to a one-liquid type moisture curing polyisocyanate prepolymer.
2) Prior Art
Hitherto, polyurethane has been used in a wide range since it exhibits excellent water resistance, excellent chemical resistance, good adhesion to a substrate and excellent mechanical properties in various sealing materials, water proof agents, coating materials, coating agents; adhesives and paving materials.
Polyurethane has been used in a wide range as so-called two-liquid type polyurethane composition in which reaction cure is usually performed by mixing main ingredient with a curing agent. However, use of such composition causes troubles in handling due to mixing of two liquid. Thus, recently, one-liquid type moisture curing polyurethane compositions in which troubles in handling due to mixing of two liquids have been overcome, e.g., as described in Japanese Patent Kokai (Laid-open) No. 57-94056, a polyurethane composition to cure a polyisocyanate prepolymer having NCO group on terminal with moisture in the atmosphere have been increased.
However, conventional one-liquid type moisture curing polyisocyanate prepolymer exhibits poor curing property in which its cured surface after moisture curing grows sticky over a long time to adhere dusts to contaminate its surface and furthermore does not provide satisfactory mechanical properties and its weather resistance also is insufficient. Usually, aromatic polyisocyanate has been used.
Thus, in order to improve contamination of surface, mechanical properties and weather resistance, various researches and developments directed to one-liquid type moisture curing polyisocyanate prepolymer have been performed. For example, Japanese Patent Kokai (Laid-open) No. 1-268769 discloses a moisture curing type polyol modified isocyanate composition obtained by reaction of long chain polyol having the number of functional group of 2 and an average molecular weight of 500 to 6000 and short chain polyol having the number of functional group to 2 to 8 and an average molecular weight of 62 to 400 and polyisocyanate. Japanese Patent Kokai (Laid-open) No. 3-247617 discloses a moisture curing polyurethane composition with isocyanate group on terminal composed of long chain polyol, linear chain aliphatic glycol having a molecular weight of 62 to 300 and organic polyisocyanate. However, aforementioned prior arts has not yet attained to uncontamination of surface and satisfactory mechanical properties and weather resistance is yet insufficient.
Japanese Patent Kokai (Laid-open) No. 5-17553 discloses a moisture curing type urethane composition comprising urethane prepolymer obtained by reaction of monool having the number of hydroxyl group of 1 and a number average molecular weight of 350 or above, polyol and organic polyisocyanate. Japanese Patent Kokai (Laid-open) No. 3-140364 discloses a thermoplastic type polyurethane prepolymer obtainable by reaction of diol and organic diisocyanate. Japanese Patent Kokai (Laid-open) No. 7-278247 discloses a moisture curing urethane composition comprising urethane prepolymer obtainable by reaction of (meth)acrylic compound having the number of hydroxyl group of 1 to 3 or oligomer thereof, polyol and organic polyisocyanate. Aforementioned prior arts also do not provide satisfactory weather resistance.
Japanese Patent Kokai (Laid-open) No. 10-168155 discloses a polyisocyanate composition containing allophanate bond obtainable by reaction of aliphatic and/or alicyclic diisocyanate and polyol having a molecular weight of 6,000 to 30,000 (except acrylpolyol), but storage stability of reaction liquid has not sufficiently considered since various catalysts are used in the reaction in order to promote allophanate bonding and furthermore curing property, particularly curing velocity is very small since the molecular weight of polyol to be used is high and also improvement of mechanical properties is insufficient.
Likewise, Japanese Patent Kokai (Laid-open) No. 7-304724 discloses a process for producing a polyisocyanate having allophanate group and isocyanate group bonded to aliphatic and/or alicyclic radical by reacting an organic compound containing urethane group with organic polyisocyanate containing isocyanate group bonded to aliphatic and/or alicyclic radical in the presence of a tin compound, but storage stability of reaction product becomes very unstable since the tin compound is used as catalyst for the reaction.
Japanese Patent Kokai (Laid-open) No. 6-172483 discloses a moisture curing composition composed of a mixture of a copolymer of meta-isopropenyl-.alpha.,.alpha.-dimethylbenzilisocyanate, (meth)acrylic monomer and other monomer and a specific polyisocyanate compound and Japanese Patent Kokai (Laid-open) No. 6-172484 discloses a moisture curing composition composed of a mixture of a copolymer of meta-isopropenyl-.alpha.,.alpha.-dimethylbenzilisocyanate with unsaturated monomer including (meth)acrylate and a specific polyisocyanate compound and Japanese Patent Kokai (Laid-open) No. 10-102406 discloses a composition for elastic paving material comprising a rubber powdery substance, a monomer including (meth)acrylate and unchangeable to yellowness type organic (poly)isocyanate, but in the prior arts using acrylic compound, working efficiency is remarkably worsened since curing velocity is very small and cured substance thus obtained does not obtain satisfactory flexibility and elongation.
Japanese Patent Kokai (Laid-open) No. 62-252416 discloses a process for producing an oligourethane containing free isocyanate by reacting organic diisocyanate, macropolyol having a molecular weight of 500 to about 10,000 and low molecular weight branched polyol having a molecular weight of 62 to 499. Even when low molecular weight branched polyol is used, uncontamination of surface and satisfactory mechanical properties cannot be obtained and aforementioned prior art does not sufficient weather resistance.
As described above, various researches and developments directed to one-liquid type moisture curing polyisocyanate prepolymer has been performed. However, under the present situation, polyisocyanate prepolymer with excellent weather resistance, high strength, excellent mechanical properties including flexibility and elongation and good curing is not yet obtained.